Commutator electric machine



May 15, 1951 J. F. G. PETIT 2,552,853

CCMMUTATCR ELECTRIC MACHINE Filed Jan. 29, 1947 3 sheets-sheet 1 Wam-M May 15, 1951 J F, G, PETIT 2,552,863

COMMUTATOR ELECTRIC MACHINE Filed Jan. 29, 1947 3 Sheets-Sheet 2 Fig. 2

May l5, 1951 J. F. G. PETIT v 2,552,863

. CCMMUT'ATCR ELECTRIC MACHINE Filed Jan.l 29, 1947 3 Sheets-Sheet 5 Patented May 1,5, 1951 COMMUTATOR ELECTRIC MACHINE Jean Francois Gabriel Petit, Paris, France, as-

signor to Societe dExploitation de Brevets, Paris, France, a, French company Application January 29, 1947, serial No. 725,019 In France February 7, 1946 9 Claims.

The present invention relates to commutator is proportional to the number of poles of the machine. This leads, for heavy currents, to commutators of undue length when it is not possible to have a suflicient number of poles. It is known, moreover, that in the case of high speed dynamos, a large number of poles would involve unduly high iron loss.

On the other hand, in order to keep the stresses on the material within acceptable limits, the speed of the rotors is limited. By making the usual stator rotate in the opposite direction, the speed of the wires in the eld is increased, thereby increasing the power-Weight ratio, but with normal armature construction, the brushes have to be rotated at the same speed as the inductor or eld magnet which involves very considerable complication.

The present invention has for its object to obviate these drawbacks. mutator electric machine (generator, motor or rotary converter) wherein sequentially progressing armature coils are connected to sequentially progressing commutator segments or bars, with the angular progression of the latter being different from the angular progression of the corresponding armature coils, instead of being identical as occurs in normal armature structure. It follows that the potential induced in the armature is caused to progress relatively to the armature at rates which are diierent about the commutator and about the armature respectively. The respective angular progressions of the correspending commutator bars and armature coils may be characterized by their ratio m which is the ratio between the angular distance between two adjacent commutator bars and the correspending armature coils.

By means of this characteristic, it is possible, in particular and as will be seen hereinafter, to construct a machine with its field and armature rotating in opposite directions, while retaining stationary brushes. This enables a very high relative speed to be obtained between the inductor and the armature while these assemblies only rotate at -normal absolute velocities which are It consists in a com- (Cl. Ill- 252) 2 compatible with a satisfactory behaviour of the machine.

Other features will become apparent from the ensuing description with reference to the accompanying drawings which are given solely by way of example, and in which:

Fig. 1 is a diagram of the armature, the commutator and their connections, assumed to be developed flat, of a four-pole machine according to the invention;

Fig. 2 is a longitudinal section of an embodiment of this machine.

Fig. 3 is a diagram of a modication of a machine enabling the direction of operation to be reversed automatically.

According to the example of construction shown diagrammatically in Fig. 1, the core of the armature l is shown by the hatched rectangle 2. Its length 2r corresponds to the development of the circumference of the armature. Said armature is provided with coils 3 forming in the example shown a four-pole lap-winding which progresses, for example, in the direction of the arrow f1. The armature is provided with a commutator whose bars are shown at 1.

These coils 3 are successively connected to adjacent commutator bars suchwise that the angular distance of two adjacent commutator bars is diierent from the angular distance of the two corresponding coils and in a definite ratio 'm therewith. In the present instance, this ratio m has been chosen equal to 1/2. If the Winding comprises for example 22 coils, the commutator may therefore comprise 44 bars. The 22 coils distributed over the whole armature will be respectively connected to a Iirst group XY of 22 bars covering a first half of the commutator, then to a second group XY' of 22 bars covering the second half of the commutator. For this purpose, it is convenient to connect all said coils 3 to intermediate conductors which, in turn are connected to the commutator bars, which permits in the case of machines having more than two poles, as is now the case, to connect all equipotential coils to the' same intermediate conductor which thus acts as an equalizing conductor and, for this reason will be called equalizing conductor, even if the machine has only two poles. In the example shown, eleven equalizing conductors 5 (A, B, C, D, E, F, G, H, I, J, K) are provided and the eleven coils 3 contained in each double pole pitch are respectively connected to said equalizing conductors at points shown at a, b, c, cl, e, f, c, h, i, 7', 7C and.

a', b', c', d', e', f', y', h', i', k', by means of leads 4. The eleven equalizing conductors 5 are respectively connected by means of leads 6 to successive groups X, X', Y, Y' of eleven commutator bars. As a result, each two equipotential coils such as 311, and 3n are interconnected through a single equalizing conductor, such as F, the latter being in turn connected to four equally spaced commutator bars such as that shown at 1n, 111..

Another embodiment, still in the case of a four-pole field consists of a machine having seventy-four coils 3, i. e. with thirty-seven equalizing conductors, a ratio m=1/3 and 111 segments on the commutator. For each double field there are 11/2 sets of thirty-seven segments or better, three sets, the six sets of the whole commutator in that case successively comprising nineteen, eighteen, nineteen, eighteen, nineteen and eighteen segments. Said segments are connected in staggered relation to the equalizing conductors, i. e. in the first set, the first segment is connected to the rst conductor, the second to the third conductor, etc. whereas in the second set, the rst segment is connected to the second conductor, the second segment to the fourth conductor, etc., the connections in the third set being the same as in the first set and so forth, alternately.

The machine is provided by brushes spaced about the commutator, the spacing of two brushes of two different polarities such as 9 and IIJ being equal to a pole pitch multiplied by the ratio m which results in a number of possible brushes equal to 2p being the number of poles. 'I'he equipotential brushes are respectively interconnected by leads I I and I2.

The machine operates as follows:

Assume that the armature is stationary and that the poles which are represented in the drawing by their axes N1S1N2Sz, are rotated at a speed w for example in the direction of the arrow f1.

At the initial instant t, the neutral lines corresponding to the poles N1, N2 are located at tu; they correspond to the coils 3, 3', to the equaliz-y ing conductor F and to the four segments 1n, 'I'n of the commutator.

At the instant (t-l-dt) the neutral lines corresponding to the poles N1, N2 will, for example, be located at (t4-d thus advancing two slots, i. e. an angle The neutral lines thus lead to the equipotential connection H which is connected to the four commutator segments 'Ih and 'Ih.

The potential available on the commutator has progressed by an angle which is in the example shown in which If now the brushes are rotated at a speed w equal to am, a direct current is obtained; if w' is dierent from wm, alternating current of frequency so that the frequency is zero and the current obtained is therefore direct current.

The Winding described therefore makes it possible, by giving w' and appropriate speed, to adjust the current obtained to the desired frequency.

It will now be assumed that a, speed -wm (i. e. in the opposite direction to arrow f1) is imparted to the whole arrangement, the potential of the commutator will be stationary and the brushes collecting the direct current must therefore be stationary. The armature will rotate at -wm, i. e. in the opposite direction to the field `which moves at w-wm.

In the case illustrated, where the absolute values are:

This arrangement enables a dynamo, a motor or a rotary converter to be constructed with a rotary inductor and armature rotating in opposite directions, While retaining stationary brushes with m: Jf

Speed of the field is w=gg Speed of armature is- -accommodates the shaft I4 at the other end of the inductor.

The eld is electrically connected to rings 2U and 2l on which rub brushes 22 and 23 connected to the source of excitation of the machine.

The speed reducer case I8 carries planet wheels 24 which mesh, on the one hand with a sun-wheel 25 secured to the inductor shaft I4, and on the other hand with a sun-wheel 26 secured to the shaft 21 of the armature 28.

The periphery 29 of the speed reducer case is toothed and meshes with a toothed crown 3U which is locked by screws 3I or otherwise on the base of the machine, in such a manner as to enable the setting of the planet wheel shafts to be varied,y which operation has the effect of electrically varying the setting of the brushes `while they remain iixed to the bearing l1.

The armature shaft 21 is `journalled in an antifriction bearing 32. Said shaft supports at 33 one vend of the armature core 34. The other end of said core is fixed at 35 to a plate 3G journalled in fan anti-friction bearing 31.

On the armature shaft 21 is fixed the commutator 38 on which rub the brushes 9, l0. The commutator comprises segments 1 which are insulated from one another and are held by means of insulating cones 39 and 4D which are clamped by cones 4l and `42.

The equalizing conductors 5 are insulated from one another and pressed against the face 43 by a -washer 44.

Each equalizing conductor carries three equidistant inner conducting tongues which are brazed on the corresponding segments of the commutator and represent the connections yl of Fig. V1. Each of said conductors furthermore carries two diametrically opposite outer tongues 45 (in the case of course of a four-pole machine) soldered to the connections 4 which are themselves connected to the armature coils 3.

In the modification shown in Fig. 3, a, device is provided which enables the machine used as a shunt generator to build up in either direction without it being necessary to reverse its field current.

According to this embodiment, the machine, which is of the four-pole type with a ratio has a shaft 46 carrying the planet gears 24. Said shaft is terminated by a lever 41 which is adapted to move 30 between two abutments formed 'by the ends 4B, 49 of a quadrant 50 secured to the frame I3 of the machine.

Furthermore, in this figure, the positive brushes 9 are connected in parallel by a connection 5I to the line Il. Similarly, the negative brushes l0 are connected in parallel by fa connection 52 to the line I2. All these brushes are stationary relatively to the frame I 3.

The machine operates as follows:

Assume that the dynamo is rotating in the direction f1 and the anti-torque moment has driven the lever 41 against the abutment 43 into the position shown which corresponds to the required setting of the brushes for this desired direction oi' operation.

The machine is stopped. The eld retains remanent magnetism in a predetermined direction. For the dynamo to be excited as it rotates in the opposite direction, this magnetism must not be destroyed by an excitation of the armature in the opposite direction. It will therefore be necessary to shift the polarity of the armature so as to place the conductors which are influenced by a north pole under a south pole.

This operation is automatically effected by the anti-torque moment of the machine which drives the lever 41 against the abutment 49, thereby shifting the armature an angle by the travel the planet gears through an angle Thus, the dynamo Awill .always lbuild up without altering the eld connections, whatever :its direction of rotation, and ythis pecularity is very important when the driving movement is obtained from the axle of a vehicle which has to move indiscriminately in either direction.

Naturally, the position of the lever 41 imay be controlled and shifted for example proportionally to the load or the speed of the dynamo or the motor, in order to obtain an optimum electric setting of the brushes.

Of course, the invention is in no way limited to the embodiments illustrated and described which have only been chosen by way of example.

As already indicated, the ratio m may be positive or negative. The ratio m may be constant or variable, it may for example be a function f (t) of time.

On the other hand, the equalizing conductors 5 may be eliminated conditionally on equivalent connections being made between the coils 3 and the segments 1 of the commutator.

Having now described my invention what I claim as new and desire to secure by Letters Patent is:

1. In an electric machine provided with a magnetic structure adapted to produce a magnetic eld, an armature inductively associated with said magnetic structure, said armature be ing provided with a winding, a commutator and means for connecting sequentially progressing points of said winding to sequentially progressing commutator bars, the angular progression of the latter being different from the angular progre sion of the corresponding points of the winding, whereby relative motion of said armature and said magnetic field causes the induced potential to progress at different rates relatively to said commutator and said winding respectively.

2. In an electric machine provided with eld producing means, an armature and means for providing relative motion of said ield and said armature, the latter including a winding, a commutator, and means for connecting sequentially progressing equidistant points of the windings to sequentially progressing adjacent commutator bars, the angular distance of two adjacent commutator bars being diiTerent from the angular distance of the corresponding points of the winding and in a constant ratio therewith, this ratio being positive when the respectively interconnected winding points and commutator bars progress in the same direction, and negative when they progress in opposite directions, whereby relative motion of said field and armature causes the potential induced in the armature to progress relatively to said commutator and said winding at rates which are in the same ratio.

3. A dynamoelectric machine having a multiple eld and an armature with a corresponding multiple winding, a commutator and means for connecting successive coils of the winding to adjacent commutator bars, the angular distance of two adjacent commutator bars being diiferent from the angular distance of the corresponding winding coils and in a constant ratio therewith, brushes spaced about said commutator, the spacin'g of two adjacent brushes being equal to a pole pitch multiplied by said ratio, and means for imparting relative motion between said armature and said brushes on the one hand and between said eld and said brushes on the other hand, the speed of the armature relatively to the brushes and the speed of the armature relatively to the field being kept in the same ratio.

4. In a dynamoelectric machine having a field structure with at least one pair of poles, an armature provided with a lap Winding designed for the same number of poles, a commutator and means for respectively connecting sequential winding coils contained in one double pole pitch to adjacent commutator bars of at least two successive groups of commutator bars, whereby the angular distance of two adjacent commutator bars differs from the angular distance of the corresponding coils by a denite ratio, and equally spaced commutator brushes, two brushes being spaced by a distance equal to a pole pitch multiplied by said ratio.

5. In a dynamoelectric machine having'a field structure with p pairs of poles, p being at least equal to one, an armature with a lap winding designed for the same number of poles, a commutator, means for interconnecting each p equipotential coils, means for connectin T each p interconnected coils to a number of equally spaced commutator bars different from p so as to pro vide a denite ratio between the angular distance of two equipotential commutator bars and the angular distance of the two equipotcntial winding coils, and equally spaced commutator brushes, two brushes being spaced by a distance equal to a pole pitch multiplied by said ratio.

6. A dynamoelectric machine comprising a casing, a. multipole eld member and an armature both rotatable relatively to said casing, the armature comprising a multipole winding, a commutator and means for connecting successive winding coils to adjacent commutator bars, the angular distance of two adjacent commutator bars being different from the angular distance of the corresponding windings coils and in a conm stant positive ratio therewith, equally spaced commutator brushes, two brushes being spaced by a distance equal to a pole pitch multiplied by said ratio, said brushes being adjustably fixed relatively to said casing, and mechanical means for positively connecting said armature with said held member to cause them to run in opposite directions suchwise that the absolute speed of the armature and the relative speed of the armature and field are in the same ratio.

7. A dynamoelectric machine as claimed in claim 6, wherein said ratio is at most equal to one half and the armature is in the form of a hollow cylinder surrounding the field member.

8. A dynamoelectric machine as claimed in claim 6, wherein said mechanical means consists in an epicyclic gear unit including two coaxial gears interconnected through planet pinions supported by a planet carrier which in turn is mounted in said casing.

9. A dynamoelectric machine as claimed in claim 8, wherein said planet carrier is mounted loose in said casing, the latter comprising two stops adapted to cooperate with said planet carrier to limit movement thereof, said stops being angularly spaced by a distance equal to a pole pitch multiplied by said ratio.

JEAN FRANQOIS GABRIEL PETT.

REFERENCES CITED rlhe following references are of record in the le of this patent:

UNITED STATES PATENTS and 117, published ,in i906 in Berlin by Julius Springer.

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